Stack changing device

ABSTRACT

In a device for changing a sheet stack in a sheet feeder, remaining-stack bars ( 7 A,  7 B) of different thicknesses are used to improve operation. Upon combination of a remaining-stack (H) with a H. sheet-stack (S), they are placed in graduations on a pallet (P) and successively pulled from the stack area.

FIELD OF THE INVENTION

The present invention relates to sheet-fed printing machines and, moreparticularly to an improved stack changing device for sheet feeders ofsheet-fed printing machines.

BACKGROUND OF THE INVENTION

It is a known practice, in sheet feeders for sheet-fed printing pressesor other sheet-processing machines, to provide arrangements forautomated stack change. These may consist of rack-type structures,so-called remaining-stack carrying devices, which are provided withthrusting and lifting drives for the horizontal and vertical movement.Such so-called non-stop stack changers are suited, for example, duringthe printing of paper sheets, i.e. in machine running, to take overremainders of finished sheet stacks from, for example, a pallet withgrooves, and to deposit them again on a new sheet stack subsequentlyinstalled in the sheet feeder. Known devices are distinguished by highconstructive and assembly expenditure and require special constructionsof the sheet feeders. Further, devices are used here, theremaining-stack carrying device of which have a rack engaging into thegrooves of the pallet. This rack is to be removed in the joining of theremaining stack with the newly installed sheet stack as a whole betweenthe two stack parts. This involves high drive forces and places verystrong stresses on the sheets lying next to the section point.Furthermore, restraining means are to be provided which prevent ashifting of the stack parts, and, in the process, severely strain thestack edges. Furthermore, the operation of the sheet feeder itself isseverely hindered or even rendered impossible. The sheet flow isdifficult to control in the changing operation, so that waste sheetsresult again and again.

Devices have already been developed that partly avoid some of thedisadvantages described.

Thus, from DE 393 1710 C2 there is known a non-stop sheet feeder forsheet-fed rotary presses. It has a remaining-stack carrying device whichis arranged underneath a conveyor table leading from the sheet feeder tothe sheet-fed rotary press. The remaining-stack carrying device has aclosed frame on which non-stop bars are arranged, which can be driven aspiston rods of individual cylinders by means of a pressure medium, andwhich are drivable into grooves of a pallet carrying a sheet stack. Thenon-stop rods lie, in the driven-in state, on both sides of the frameand are to be removed successively from the zone of the sheet feeder.While the rods have individual drive cylinders, the patent disclosesnothing about the sequence of operation. The bridging of the gapconditioned by the non-stop bars between main stack and remaining stackis an obstacle to a faultless continuous processing in the unificationof the stacks.

From DE 4 203 500 A1 a sheet feeder is known. It has, parallel to thesheet feeder and allocated to this on the face side, an auxiliarystack-carrying device as an independent component. Then, over a commondrive, individually drivable pointed bars are provided which can beintroduced into grooves of a pallet carrying a sheet stack. The drivehas individual chain gears which are couplable onto the respectivepointed bars. For the guidance and accessibility of the chain drives,special constructive measures are required. The chain drives completelyblock the space in front of the sheet feeder, so that the latter is notaccessible. In the stack changing, it is provided to remove the pointedbars in the joining of main stack and remaining stack, first on theoutside, then in the middle and lastly in the zone between the alreadypulled pointed bars out of the stack and remaining stack, so that agentle depositing of the remaining stack of the sheet stack results.This, however, is possible with the requisite precision only in the caseof heavy materials such as sheets of metal, since the sheets bulge indifferent direction and must sink over a large gap that is formed by thepointed bars.

Finally, from DE 19520772 C1 there is known a non-stop sheet feeder forprinting presses with fork bars movable in and out. In this feeder onboth sides of the stack zone there are provided units of fork barsmovable transversely to the sheet transport direction. The fork bars arejoined with one another and are drivable in common into grooves of apallet carrying a sheet stack. From there they can take over anauxiliary stack in order to bridge the time period up to the supplyingof a new sheet stack. For the preliminary approach of the main stack andof the remaining stack before the final joining, the fork bars arerectangular in cross section and turnable about a longitudinal axis.There the fork bars thrust in first in the upright orientation, in orderto be able to carry as great a load as possible. For the approach theyare then rotated through 90 degrees, so that the main stack and theremaining stack approach the value of the thickness of the narrower sideto each other. In the turning of the fork bars measures have to be takenin order to avoid a shifting of the sheets lying next to the fork bars.This has proved in practice to be virtually unfeasible.

Further, from DAS 105 297 there is known a sheet feeder with severalstack-lifting mechanisms. It has a fork-shaped remaining-stack carryingdevice, which is provided with remaining-stack bars slidable intogrooves of a pallet. The device makes possible the take-over of aremainder of a sheet stack from the pallet for the continuous feeding ofthe sheets while a new sheet stack is installed into the sheet feeder.The remaining-stack device is connected with a separate liftingmechanism parallel to the main-stack lifting mechanism inside the sheetfeeder, so that the remaining stack is continuously liftable. Theoperating range of the remaining-stack carrying device is restricted.The remaining-stack carrying device hampers access to the sheet feeder.

OBJECTS AND SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide an improved stack changing device which overcomes the problemsassociated with prior art designs.

A more specific object of the present invention is to provide a stackchanging device which allows for simple and continuous stack changingwith undisturbed sheet transport and no wasted paper.

The present invention provides these and other advantages and overcomesthe drawbacks of the prior art by providing a stack changing devicewhich utilizes an improved method and device for receiving aremaining-stack and transferring the remaining stack to a newly fed-insheet stack.

It is advantageous that carrying and spacing bars movable independentlyfrom one another are provided in the device, which are pulled out of thestack zone not simultaneously but intermittently for the unburdening ofthe sheet material. There can be provided preferably a different heightof the two types of bars, which generates a smooth depositing movementof the remaining stack on the sheet stack. The pulling movement of thebars has no influence on the remaining stack resting on it, so that thedirectly affected paper sheets are spared, since only slight or noretaining forces are required. In particular the continuous removal ofthe remaining-stack bars from inward, outward and in two states makespossible a gentle depositing of the remaining stack on the sheet stack.Moreover, it is advantageous to make the remaining-stack bars, accordingto type, of different length, so that an improved working run-offresults.

These and other features and advantages of the invention will be morereadily apparent upon reading the following description of preferredexemplary embodiments of the invention and upon reference to thedrawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an illustrative embodiment of a sheetfeeder constructed in accordance with the present invention,

FIG. 2 is a plain view of a sheet feeder,

FIG. 3 is a plain view of a stack-changing device of the sheet feeder ofFIG. 1,

FIG. 4 is a plan view showing the stack-changing device of FIG. 3 takingover a remaining stack, and

FIGS. 5 to 8 are schematic side elevational views showing anillustrative stack changing process according to the present invention,and

FIG. 9 is an enlarged partial plan view showing the stack-changingdevice during the stack change.

While the invention will be described and disclosed in connection withcertain preferred embodiments and procedures, it is not intended tolimit the invention to those embodiments. Rather it is intended to coverall such alternative embodiments and modifications as fall within thespirit and scope of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 there is represented a sheet feeder 2 connected with asheet-processing machine, for example with a. sheet-fed printing press1. In the sheet feeder 2 a sheet stack S is installed for processing.The sheet stack S can be lifted in the rhythm of the sheet processing bymeans of a main-stack lifting unit which is not represented in detailhere. The sheets of the stack S are taken one by one or singled from itsupper side and fed to the sheet-fed printing press 1 as a sheet stream.In the sheet feeder 2 there is provided a sheet-singling arrangement 4,which is provided with a whole number of multiple operating elements forformat-dependent adjustments and for adjustments of the supplying witheither suction or blast air. The operating elements serve for theattuning of the various functions of the sheet-singling device 4 to theproper transport of the sheets from the sheet feeder 2 to the sheet-fedprinting press 1. In the sheet feeder 2 there is arranged, further, aremaining-stack carrying device 3, which is assigned to the face sideaway from the sheet-fed printing press 1 of the sheet feeder 2. Theremaining-stack carrying device 3 is provided with a rack or frame 6, inwhich the remaining-stack bars 7 are stored longitudinally shiftably. Bymeans of the frame 6, the remaining-stack carrying device 3 is suspendedon a remaining-stack lifting unit 5. The remaining-stack lifting unit 5is indicated here only in its position, but not in details. Theremaining-stack lifting unit 5 serves to hold a remaining stack H in thesheet feeder 2 and to raise it in the rhythm of the sheet processing.For this reason the remaining-stack lifting unit 5 is also controllablesynchronously with the main stack-lifting device. The remaining-stacklifting unit 5 consists of vertical guide rails 8 connected with thesheet feeder 2, on which (rails) the frame 6 is guided, and has, forexample, lift chains by means of which the remaining-stack carryingdevice 3 is raisable or lowerable.

In FIG. 2 the sheet feeder 2 is shown in a top view. Upon the sheetfeeder 2 there follows in the sheet running direction indicated byarrows, a so-called conveyor table 20, over which the sheet streamgenerated by the singling is transported-to the sheet-processingmachine, for example the printing press 1. Further, the position of thesheet-singling device 4 is recognizable in allocation to the rear edgeof the sheet stack S. The orientation of the remaining-stack bars 7 isrepresented in its arrangement in respect to the sheet feeder 2, onlythe two outer remaining-stack bars 7 being represented, and the othersbeing indicated with effect lines. The position shown is, for example,the readiness position before the initiation of a changing process, orthe waiting position outside of the operating range of the sheet feeder2. The remaining-stack bars 7 are guided there within theremaining-stack carrying device 3, so that in the position shown theyoccupy a horizontal position outside the zone of the sheet feeder 2. Theremaining-stack carrying device 3 with its frame 6 is guided by means ofthe guide rails 8 on the sheet feeder 2 and is vertically movable. Theremaining-stack lifting unit 5 is again indicated only in its positionand is located on the upper side of the guide rails 8, for example onthe frame of the sheet feeder 2, it engages from there on the frame 6 ofthe remaining-stack carrying device 3 and moves this stack upward anddownward on the guide rails 8.

From FIG. 1 it is evident that the remaining-stack carrying device 3 isinstalled by means of the guide rails 8 directly into the sheet-feeder2. On the one hand, the remaining-stack lifting unit 5 is movableliftably and lowerably during the supplying of the printing press 1 withsheets and, on the other hand, the remaining-stack carrying device 3 ismovable outside of the processing zone for the stack change proper.Through this arrangement in the sheet feeder 2, the latter is very wellaccessible from its face-side operating side.

In FIG. 3 there is shown a complete representation of theremaining-stack carrying device 3. The frame 6 is vertically guided onthe guide rails 8. In the frame 6 in a front carrying rail 9 there areguided the remaining-stack bars 7 in the form of carrying bars 7A andspacer bars 7B. On a rear carrying rail 10 there is arranged a pullingdrive 11 for the singled pulling of the carrying bars 7A and spacingbars 7B. It will be appreciated by one skilled in the art that variousknown pulling drives may be used for individually pulling the carryingbars 7A and spacing bars 7B, including gear drive chains such as shownin the above-referenced DE 4203 500 A1 or individual drive cylinders,such as shown in the above-referenced DE 39 171 0 C. Moreover, as willbecome apparent herein, such known drives may be operated tosimultaneously pull more than one carrying bar 7A or spacing bar 7B at atime.

In FIG. 3, the carrying bar 7A and spacing bar 7B are shown in thewaiting position. Further, there are provided on both sides drives 12for the longitudinal shifting of the rear carrying rail 10 on guiderails 13 of the frame 6. The drives 12 determine the position of therear carrying rail 10 at the rear end or within the frame 6. The frontcarrying rail 9 is firmly joined with the frame 6. The carrying bars 7Aand the spacing bars 7B are of different height. The carrying bars 7A,for example, are about twice as high as the spacing bars 7B. By heightthere is meant the extension of the carrying bars 7A or spacing bars 7B,respectively, perpendicular to the extended plane of the remaining-stackcarrying device 3. The effect of this measure will still be thoroughlyshown in the following representations.

The carrying bars 7A and spacing bars 7B can be of equal length. In apreferred form of execution, however, the carrying bars 7A are longerthan the spacing bars 7B. The carrying bars 7A serve, in the takeover ofa remaining-stack H, first of all for the load reception, and they areto be dimensioned correspondingly, in which case the load is to be ledoff into a further carrying means (see FIG. 4).

In FIG. 4 the remaining-stack carrying device 3 is shown functioning.The carrying bars 7A, as well as the spacing bars 7B are thrust forwardby means of the drives 12 together with the rear carrying rail 10opposite the front carrying rail 9 and introduced into grooves of apallet P carrying the sheet stack S. Front carrying rail 9 and rearcarrying rail 10 with the pulling drive 11 now lie parallel in front ofthe pallet P which carries a remainder of a sheet stack S, the so-calledremaining-stack H. The pallet P and the remaining-stack H are nottouched there by the front carrying rail 9. The longer and highercarrying bars 7A lie on a remaining-stack lifting rail 14 on the frontend (as seen in sheet running direction) in the sheet feeder 2. Thisremaining-stack lifting rail 14 is coupled with a lifting drive andprovided for the support of the carrying bars 7A as well as theirlifting movement during production. The remaining-stack lifting rail 14and the remaining-stack lifting unit 5 are both connected for thispurpose with the main stack lifting unit of the sheet feeder 2, or atleast mechanically or controlably coupled with one another in suchmanner that in the stack processing, especially, however, in thebringing together of the remaining-stack H with a new sheet stack S,they can be lifted synchronously.

From FIG. 4 it is further to be learned that in the position representedof the remaining-stack carrying device 3 with carrying bars 7A and thespacing bars 7B thrust into the pallet P, the space inside the frame 6is free and the frame 6 is open to the rear. For handling, it can be ofimportance that the carrying bars 7A and spacing bars 7B can be fittedinto the grooves of the pallet P already early, i.e., long before theactual required changing operation. The remaining-stack carrying device3 can then be lifted in common with the sheet stack S until the stackchange actually must occur. Then the remaining-stack H need still belifted only from the pallet P. When the remaining-stack bars 7 are againpulled, i.e., the stack unification has taken place, the remaining-stackbars 7 can immediately be driven again into the new pallet P.

The actual operation of the stack change is represented via steps inFIGS. 5 to 8.

A precondition is that in the sheet feeder 2 a sheet stack S iscontinuously raised during the processing, i.e. singling of the sheetson the upper side of the sheet stack S and their transport in the sheetstream to the printing press 1. There, a point is reached at which thereis present only a remaining stack H of the sheet stack S that has apredetermined height. In dependence on the processing speed there stillremains then only a certain span of time until the remaining stack H islikewise used up. Within this span of time, a new stack sheet S must beavailable in the sheet feeder 2, otherwise the operating process must beinterrupted. For this reason at the predetermined time point, whichdepends on the height of the remaining stack H from the sheet stack S,the course to the stack change is set in operation.

In FIG. 5, it is schematically shown how a remaining stack H,respectively the remainder of the sheet stack S, is lifted from thepallet P. This occurs by the means that the remaining-stack bars 7 areslid into the grooves of the pallet P and the pallet P is lowered bymeans of the main stack lifting mechanism. Then, at first, only thehigher and lengthened carrying bars 7A, resting as represented in FIG. 4on the remaining-stack lifting rail 14, carry the remaining stack H. Thelower spacing bars 7B lie free, but guided by the carrying rails 9, 10.The carrying rails 9 and 10 are, at this point in time, parallel to oneanother in a compact position with small spacing with respect to therear edge of the remaining stack H. It can be provided that in relationto the inside-lying stack middle, the thinner spacing bars 7B arelengthened for switching functions and likewise rest on the remainingstack lifting rail 4. Likewise, all the spacing bars 7B can be made asemplaceable on the remaining-stack lifting rail 14.

In FIG. 6 it is represented how a new sheet stack S is raised fromunderneath against the remaining-stack carrying arrangement 3. There thecarrying bars 7A stand in contact from above with the remaining-stack Hand from underneath with the sheet stack S. The carrying bars 7A aretherefore firmly guided. Here it is to be considered from the viewpointof control techniques, that the lifting movement of remaining stack Hand sheet stack S, as already executed further above, must besynchronized. In the running of the sheet stack S against the carryingbars 7A, for example, a sensor in the remaining-stack carrying bars 7A,for example, a sensor in the remaining-stack rail 14 may initiate thesynchronization of the lifting movements of remaining stack H and sheetstack S, and also the now beginning pulling movement. In a variant alsothe inner spacing bars 7B can already stand in contact with the twostack surfaces. Then exclusively in the middle no carrying bars 7A wouldbe present and the remaining-stack H would already be lowered there bythe height difference between the carrying bars 7A and spacing bars 7B.

In FIG. 7 it is shown that the thicker carrying bars 7A were alreadyremoved. This process is feasible, for example, by means of individualdrives, but there can also be spanned drive connections, for example,pulling means, between the pulling drive 11 arranged on the rearcarrying rail 10 and the carrying bars 7A or the spacing bars 7B. Forthe pulling, the carrying bars 7A are then connected individually withthe pulling drive 11, in which operation the carrying bars 7A, forexample, are directly freed in pairs and thus also pulled in pairs bymeans of the pulling drive 11 out of the space between remaining stack Hand sheet stack S until they again lie on the rear carrying rail 10. Thepulling sequence is preferably controlled in such manner that thecarrying bars 7A are pulled in the sequence from the middle of the stackoutward. There consequently the remaining stack H sinks slowly outwardfrom the stack middle to the stack edges onto a second plane which isdefined by the spacing bars 7B. This position is represented in FIG. 7:in the simplest case the spacing bars 7B are shorter than the carryingbars 7A and in the shown position they execute, as it were, still only acontrol function for the continuous stack unification, since they nolonger rest on the remaining-stack lifting rail 14 and thus also cannotdivert any load. It can also be provided, however, that the spacing bars7B are of equal length with the carrying bars 7A and then also rest onthe remaining-stack lifting rail 14. This can serve, for example, topick up the end of the pulling movement on the remaining-stack liftingrail 14 executed as a scanning rail and does impair the control functionfor the stack unification. Only the time expenditure for the pullingbecomes somewhat greater.

In FIG. 8, finally, there is represented the initiation of theconclusion of the pulling movement. Now in the same rhythm, i.e.preferably in pairs, the thin spacing bars 7B which, after all, stillonly separate the remaining stack H from the sheet stack S, but nolonger exercise any lifting or carrying function any more, for example,likewise are pulled outward in pairs from the stack middle to the stackedges. There the auxiliary stack H now again, in likewise continuousmovement, comes to lie on the sheet stack S, without the result that theremaining stack H would move with respect to the sheet stack S andthereby be jammed by forced means or would have to be fixed in relationto the sheet stack S. This holds both in the direction of the pullingmovement of the remaining-stack bars 7 toward the rear stack border aswell as in transverse direction thereto, toward the later stack edges.The stack change is therewith concluded after the joining of remainingstack H and sheet stack S, and the remaining-stack carrying device 3 canbe repositioned.

In FIG. 9, the connection of the pulling movement to the arrangementinside the sheet feeder 2 is once again clarified. The carrying bars 7Aand the spacing bars 7B lie alternately in grooves of a pallet P (inwhich context one must imagine oneself as lying on the webs between thegrooves of the pallet P in the normal manner of the sheet stack S). Thecarrying bars 7A rest there on the remaining-stack lifting rail 14. Thesame holds in the illustrated case for the inner spacing bars 7B, whichhave only half the height of the carrying bars 7A. The pulling processof the carrying bars 7A begins with the thicker carrying bars 7A lyingnearest the middle of the stack, which bars, as represented, are pulledas a pair. There the auxiliary stack H in this zone comes to lie slowlyon the thinner spacing bars 7B. The pulling of the thicker carrying bars7A, and then of the thinner spacing bars 7B, occurs smoothly and inclose time sequence, but always separately from one another. For thisthere is provided a device for controlling the pulling movement. Thiscan be integrated directly into the pulling drive 11 for the carryingbars 7 a or spacing bars 7B, or it can act over further control means onthe pulling drive of each individual carrying bar 7A or spacing bar 7B.

The stack change proceeds, therefore, as follows:

I. On reaching a minimum height of the sheet stack S the stack-changingprocess is started.

II. The carrying bars 7A and the spacing bars 7B are slid in common fromthe frame 6 into the grooves of the pallet P underneath the sheet stackS, the sheet stack S remaining free on the rear side toward theremaining stack carrying device 3.

III. The carrying bars 7A are slipped-under and raised from theremaining-stack lifted rail 14 until the remaining stack H is borne bythe carrying bars 7A.

IV. The pallet P is lowered and removed from the sheet feeder 2.

V. The remaining-stack is continuously further raised by means of theremaining-stack lifting unit 5 for the singling of the sheet.

VI. A new sheet stack S is installed in the sheet feeder 2 and is liftedby means of the main stack-lifting mechanism.

VII. On contacting of the upper side of the sheet stack S with theunderside of the carrying bars 7A the pulling operation of the carryingbars 7A is initiated.

VIII. The carrying bars 7A are pulled out singly or in pairs from insideoutward between remaining stack H and sheet stack S.

IX. The remaining stack H is deposited continuously from the insideoutward on the spacing bars 7B.

X. The remaining-stack lifting rail 14 becomes free, the remaining-stackcarrying device 3 no longer takes on any load, the remaining spacingbars 7B still have only a control function for the stack unification.

XI. The spacing bars 7B are continuously drawn out from the insideoutward between remaining-stack and sheet stack S.

XII. The remaining-stack H is deposited continuously from the insideoutward on the upper side of the sheet stack S.

In a modified version of the run-off the procedure is as follows:

I. The remaining-stack carrying device 3, after the pulling of thecarrying bars 7A and spacing bars 7B, is immediately lowered to thestack lower edge of the new sheet stack S.

II. The carrying bars 7A and spacing bars 7B are introduced into thegrooves of the pallet P, their thrusting-in path being less than thetotal thrusting-in path.

III. The remaining-stack carrying device 3 is lifted load-freesynchronized with the sheet stack S.

IV. On reaching the limit height of the sheet stack S the carrying bars7A and the spacing bars 7B in the frame are slid in, up to the totalsliding-in length (the rear side of the sheet stack S remaining freetoward the remaining-stack carrying device 3).

V. The remaining stack lifting rail takes over the carrying bars 7A.

VI. The run-off is continued as described above.

The entire run-off has the advantage that the remaining-stack Hcontinuously approaches the sheet stack S, so that no jump points arisein the removing of the remaining-stack bars 7, which have a troublesomeeffect on the sheet singling or in the moving-out of the sheets from thesheet feeder 2, or that could even interrupt the operating run-off. Thisholds first of all for the steady follow-up of the upper side of thestack with respect to the sheet singling arrangement, where a spacing isto be maintained within a tolerance range. Further this holds for themoving-off of sheets after the singling, since on the front edge of thesheet stack S or remaining-stack H there are provided control means, forexample a so-called sheet flap, which frees or blocks the sheet path.Here, too, a determined height tolerance is to be maintained, so thatthe sheet front edge in the moving-off does not strike through thethrusting movement, and is therewith upset or upended.

The pulling movement, in each case when only two remaining-stack bars 7simultaneously likewise cannot affect the position of the sheets in thesheet plane in the stack unification zone. For this reason it ispossible to dispense with retaining measures which might damage thesheet.

In a further form of execution, it can provided not to use all of theremaining-stack carrying bars 7. Thus the spacing bars can be omitted inthe case of very thick sheet materials, which in consequence of theirstability sink only slowly into the interspace that becomes ever largerbetween the sheet stack S and the remaining stack H. Therewith thechanging process is accelerated, since time for the pulling of thespacing bars 7B is saved.

Likewise, carrying bars 7A can be omitted in pairs in the middle of thestack, so that the auxiliary stack H there sinks immediately onto thespacing bars 7B. The adjusting process on the stack surface in relationto the singling device can be supported by an at first slow lowering ofthe pallet P.

For these measures the corresponding remaining-stack bars 7 do not haveto be removed. It suffices to uncouple or to block the correspondingdrive means. These remaining-stack bars 7 then, of course, are likewisenot driven into the grooves of the pallet P before the stack change.

What is claimed is:
 1. A process for automatically and continuouslychanging a sheet stack in a sheet feeder of a sheet-processing machineincluding a remaining-stack carrying device having remaining-stack bars,the sheet stack having a pair of opposing stack edges and a middle areainterposed between the opposing stack edges, the stack changing processcomprising the steps of: temporarily receiving a remaining stack from apallet on the remaining-stack bars by sliding the remaining-stack barsunderneath said remaining stack from a common side of the stack into astack position, continuously raising said remaining stack with theremaining-stack bars, and depositing said remaining stack on a newlyfed-in sheet stack which has been moved into position below saidremaining stack by sequentially removing the remaining-stack bars fromthe stack position starting with at least one of the remaining-stackbars in the middle area of the sheet stack and then progressivelyremoving others of the remaining stack bars progressing outwardly to theremaining-stack bars adjacent the opposing stack of the sheet stack. 2.The process of claim 1 including sliding the remaining stack barsunderneath said remaining stack from a rear side of the stack inrelation to a direction in which sheets are removed from the stack bythe sheet feeder.
 3. The process of claim 1 including removing theremaining stack bars in pairs.
 4. A process for automatically andcontinuously changing a sheet stack in a sheet feeder of asheet-processing machine including a remaining-stack carrying devicehaving remaining-stack bars, the sheet stack having a pair of opposingstack edges and a middle area interposed between the opposing stackedges, the stack changing process comprising the steps of: temporarilyreceiving a remaining stack from a pallet on the remaining-stack bars bysliding the remaining-stack bars underneath said remaining stack from acommon side of the stack into a stack position with said remaining stackresting on a first set of the remaining-stack bars in a position above asecond set of the remaining-stack bars, continuously raising saidremaining stack with the remaining-stack bars and depositing saidremaining stack on a newly fed-in sheet stack which has been moved intoposition below said remaining stack by sequentially removing the firstset of remaining stack bars from the stack position starting with atleast one of the remaining stack bars of the first set arranged in themiddle area of the sheet stack and progressing outwardly to remainingstack bars of the first set adjacent side edges of the sheet stack suchthat the remaining stack is deposited on the second set of remainingstack bars, and then sequentially removing the second set of remainingstack bars starting with at least one of the remaining stack bars of thesecond set arranged in the middle area of the sheet stack andprogressing outwardly to remaining stack bars adjacent side edges of thestack such that the remaining stack is thereupon joined with the newlyfed-in sheet stack.
 5. The process of claim 4 including sliding theremaining stack bars underneath said remaining stack from a rear side ofthe stack in relation to a direction in which sheets are removed fromthe stack by the sheet feeder.
 6. The process of claim 4 includingremoving the remaining stack bars in pairs.
 7. The process of claim 4including sliding said carrying bars a greater distance into said stackthan said spacing bars.
 8. A device for changing a sheet stack in asheet feeder of a sheet processing machine, the stack changing devicecomprising: a main stack lifting mechanism for raising and lowering of asheet stack having opposing stack edges and a middle area, aremaining-stack carrying device including remaining-stack bars fortemporarily receiving a remaining stack and transferring said remainingstack to a newly fed-in sheet stack, a drive mechanism for slidablymoving said remaining stack bars underneath a remaining stack of sheetsfrom a common side of the remaining stack, a remaining-stack liftingmechanism for raising the remaining-stack carrying device, and saiddrive mechanism being operable for sequentially removing the remainingstack bars from the remaining stack starting with at least one of theremaining stack bars in the middle area of the sheet stack andprogressing outwardly to the remaining stack bars adjacent the opposedstack edges of the sheet stack.
 9. The stack changing device accordingto claim 8 in which said remaining stack bars comprise carrying bars andspacing bars, said carrying bars and spacing bars being arranged inalternating relation to each other, and said drive mechanism beingoperable for sequentially removing the carrying bars and thensequentially removing said spacing bars.
 10. The stack changing deviceaccording to claim 9 in which said spacing bars have upper sheetreceiving surfaces disposed below the upper sheet receiving surfaces ofsaid carrying bars.
 11. The stack changing device according to claim 9in which said carrying bars are longer in length than said spacing bars.12. The stack changing device according to claim 9 wherein each of thecarrying bars have a thickness and a length which is different than thethickness and length of each of the spacing bars.
 13. The stack changingdevice according to claim 12 wherein each of the carrying bars isrelatively longer than each of the spacing bars.
 14. The stack changingdevice according to claim 9 wherein each of the spacing bars has athickness and each of the carrying bars has a different relativethickness.
 15. The stack changing device according to claim 14 whereineach of the carrying bars is relatively thicker than each of the spacingbars.
 16. A device for changing a sheet stack in a sheet feeder of asheet-processing machine, the stack changing device comprising: a mainstack lifting mechanism for raising and lowering of a sheet stack havinga pair of opposing stack edges and a middle area interposed between theopposing stack edges, a remaining-stack carrying device includingremaining-stack bars having different relative thicknesses fortemporarily receiving a remaining stack and transferring said remainingstack to a newly fed-in sheet stack, a drive mechanism for slidablymoving said remaining stack bars underneath a remaining stack of sheetsfrom a common side of the remaining stack, a remaining-stack liftingmechanism for raising the remaining-stack carrying device, and saiddrive mechanism being operable for sequentially removing the relativelythicker remaining stack bars such that the remaining sheet stack isdeposited on the relatively thinner remaining stack bars, and thensequentially removing the relatively thinner remaining stack bars suchthat the remaining stack is thereupon deposited on a newly fed-in sheetstack.
 17. The stack changing device according to claim 16 wherein theremaining-stack bars have two different relative thicknesses and arearranged in an alternating symmetrical arrangement based on theirthickness over the width of the remaining-stack carrying device.
 18. Thestack changing device according to claim 16 wherein the remaining-stackbars have two different relative thicknesses and lengths and arearranged in an alternating symmetrical arrangement based on theirthickness and length over the width of the remaining-stack carryingdevice.
 19. The stack changing device according to claim 16 wherein theremaining-stack bars comprise carrying bars and spacing bars and each ofthe carrying bars are relatively thicker than each of the spacing bars.20. The stack changing device according to claim 16 wherein theremaining-stack bars comprise carrying bars and spacing bars and thatthe carrying bars are relatively longer than the spacing bars.
 21. Adevice for changing a sheet stack in a sheet feeder of asheet-processing machine, the stack changing device comprising: a mainstack lifting mechanism for raising and lowering of a sheet stack havinga pair of opposing stack edges and a middle area interposed between theopposing stack edges, a remaining-stack carrying device havingremaining-stack bars including first remaining stack bars having arelatively high stack receiving surface and second remaining stack barshaving a relatively low stack receiving surface, a drive mechanism forslidably moving said remaining stack bars underneath a remaining stackof sheets from a common side of the remaining stack, a remaining-stacklifting mechanism for raising the remaining-stack carrying device, andsaid drive mechanism being operable for sequentially removing the firstremaining stack bars such that the remaining stack is deposited on thesecond remaining stack bars, and then sequentially removing the secondremaining stack bars such that the remaining stack is thereupondeposited on a newly fed-in sheet stack.